A facile preparation of novel positively charged MOF/chitosan nanofiltration membranes

A novel positively charged nanofiltration (NF) membrane was fabricated by incorporating metal-organic frameworks (MOFs) into chitosan polymeric matrix for enhanced removal of multivalent cations. The synthesized MOFs, NH 2 -MIL-101(Al) and NH 2 -MIL-101(Cr), could be homogeneously dispersed in the chitosan polymeric matrix. The morphologies of MOFs had a significant influence on the permeability of NF membranes. NF membrane filled with NH 2 -MIL-101(Al) with rod-like structure attained two times higher flux but similar rejection compared with that filled with NH 2 -MIL-101(Cr) with grainy structure. The effect of MOF loadings (NH 2 -MIL-101(Al)) on the membrane performance were evaluated by XRD , FTIR and SEM. These positively charged MOF/chitosan NF membranes were able to reject up to 93.0% of MgCl 2 , and the salt rejection followed the order of MgCl 2 >CaCl 2 >NaCl>Na 2 SO 4 .